Double-focal-length objective lens optical system with continuous large depth of field, objective lens and aiming equipment

Abstract

The invention discloses a double-focal-length objective lens optical system with continuous large depth of field, an objective lens and aiming equipment. The optical system comprises a front fixing group, a zooming group and a rear fixing group which are sequentially arranged in the direction from an object space to an image space, the zooming group can move along the optical axis, and when the zooming group is located at a first position and a second position, the objective lens has a first gear focal length and a second gear focal length; wherein the first position is closer to the front fixing group than the second position. According to the invention, two-gear zooming is carried out by moving the zooming group, and the depth-of-field ranges under two gears of focal lengths are partially overlapped through a special optical system design, so that continuous depth-of-field in a relatively large range is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical technology, in particular to a dual focal length objective optical system with continuous large depth of field, an objective and a sighting device. BACKGROUND

[0002] The conventional single field of view objective optical system cannot meet the demand that the observation and sighting system is in a long focal length and narrow field of view state when searching and detecting targets, and is in a short focal length and wide field of view state when identifying and tracking targets. In modern warfare, the application range and threat degree of unmanned aerial vehicles (UAVs) are increasing day by day, and the traditional air defense weapon system has many limitations in the face of the threat brought by UAVs. The observation and sighting instrument with the characteristics of multi-field of view, large depth of field and high definition can endow a single soldier or a small group of combat forces with the ability to attack UAVs, and has unique advantages in dealing with ordinary threat levels and close-range UAVs, and is an important part of the anti-UAV combat system.

[0003] The fixed focus objective has the defects of limited depth of field of the fixed focus lens, untimely focusing operation and sacrifice of imaging image quality by electronic amplification. The continuous zoom lens has the problems of low resolution and easy loss of targets in zoom operation, and the continuous zoom optical system has a large axial size, a complex structure and a large difficulty in processing and assembly. Therefore, it is very important to develop an objective with a large depth of field range, high definition, consideration of different fields of view and different object distances, and convenient gear switching. SUMMARY

[0004] The present application aims to provide a dual focal length objective optical system with continuous large depth of field, an objective and a sighting device to adapt to clear observation of objects in a specific object distance range.

[0005] To solve the above technical problems, the present application provides a dual focal length objective optical system with continuous large depth of field, comprising a front fixed group, a zoom group and a rear fixed group arranged in order from the object side to the image side; the zoom group can move along the optical axis, and the objective has a first gear focal length f 短焦 and a second gear focal length f 长焦 when the zoom group is located at a first position and a second position respectively; wherein the first position is closer to the front fixed group than the second position; The focal length f 前固定组 of the front fixed group satisfies: 1.00 < f 前固定组 / f 长焦 < 1.75; The focal length f 变焦组 of the zoom group satisfies: -0.67 < f 变焦组 / f 长焦 < -0.33; The focal length f 后固定组 of the rear fixed group satisfies: 0.20 < f 后固定组 / f长焦 <0.60; the first gear focal length f 短焦 , the second gear focal length f 长焦 satisfies: f 长焦 / f 短焦 ≥2; 25mm < f 短焦 < 35mm; 50mm < f 长焦 < 70mm; the F number of the objective lens is greater than or equal to 2.8.

[0006] According to the above scheme, the front fixed group includes a front fixed group cemented lens and a front fixed group single lens; the front fixed group cemented lens is formed by cementing a positive lens and a negative lens; and the front fixed group single lens is a positive lens.

[0007] According to the above scheme, the front fixed group single lens is a spherical lens.

[0008] According to the above scheme, the zoom group includes a zoom group cemented lens and a zoom group single lens; the zoom group cemented lens is formed by cementing a positive lens and a negative lens; and the zoom group single lens is a negative lens.

[0009] According to the above scheme, the zoom group single lens is a spherical lens.

[0010] According to the above scheme, the rear fixed group includes a diaphragm, at least one rear fixed group cemented lens, and a plurality of rear fixed group single lenses; the rear fixed group cemented lens is formed by cementing a positive lens and a negative lens.

[0011] According to the above scheme, the plurality of rear fixed group single lenses includes an aspherical lens.

[0012] According to the above scheme, all the lenses in the optical system are glass lenses.

[0013] The application further provides a dual focal length objective lens with continuous large depth of field, which includes the optical system described above.

[0014] The application further provides a dual focal length sighting device with continuous large depth of field, which includes the objective lens described above.

[0015] Advantages The optical system of the present application realizes fast zooming through the axially movable zoom group, and has long and short focal lengths, so that the target observation of long and short distances can be adapted without designing two sets of optical systems with different focal lengths, and the complexity of the objective optical system is reduced. In addition, the focal planes of the optical system at the two focal lengths are coplanar through special setting of the focal lengths of the optical components in the optical system and the two focal lengths of the optical system, so that the imaging is stable. At the same time, the depth of field of the two focal lengths is overlapped, that is, there is a certain distance of continuous depth of field coverage, and clear imaging can be realized in the depth of field coverage range, which widens the observation range. In addition, through the limitation of the F number, it is ensured that the optical system has sufficient light amount at different focal lengths, which is beneficial to improve the image quality.

[0016] Further, all the lenses in the present application are glass lenses, which effectively reduces the production cost of the optical system. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a different focal length schematic diagram of the dual focal length objective optical system with continuous large depth of field of the embodiment one of the present application; Figure 2 is a long focal length position transfer function diagram of the dual focal length objective optical system with continuous large depth of field of the embodiment one of the present application; Figure 3 is a short focal length position transfer function diagram of the dual focal length objective optical system with continuous large depth of field of the embodiment one of the present application; Figure 4 is a long focal length position spot diagram of the dual focal length objective optical system with continuous large depth of field of the embodiment one of the present application; Figure 5 is a short focal length position spot diagram of the dual focal length objective optical system with continuous large depth of field of the embodiment one of the present application; Figure 6 is a different focal length schematic diagram of the dual focal length objective optical system with continuous large depth of field of the embodiment two of the present application; Figure 7 is a long focal length position transfer function diagram of the dual focal length objective optical system with continuous large depth of field of the embodiment two of the present application; Figure 8 is a short focal length position transfer function diagram of the dual focal length objective optical system with continuous large depth of field of the embodiment two of the present application; Figure 9 is a long focal length position spot diagram of the dual focal length objective optical system with continuous large depth of field of the embodiment two of the present application; Figure 10 is a short focal length position spot diagram of the dual focal length objective optical system with continuous large depth of field of the embodiment two of the present application; Figure 11is a different focal length schematic diagram of the bifocal objective optical system with continuous large depth of field of embodiment three of the present application; Figure 12 is a long-focus position transfer function diagram of the bifocal objective optical system with continuous large depth of field of embodiment three of the present application; Figure 13 is a short-focus position transfer function diagram of the bifocal objective optical system with continuous large depth of field of embodiment three of the present application; Figure 14 is a long-focus position spot diagram of the bifocal objective optical system with continuous large depth of field of embodiment three of the present application; Figure 15 is a short-focus position spot diagram of the bifocal objective optical system with continuous large depth of field of embodiment three of the present application.

[0018] In the figure: 101, first cemented lens; 102, third lens; 103, fourth lens; 104, second cemented lens; 105, third cemented lens; 106, ninth lens; 107, tenth lens; 108, fourth cemented lens; 1011, first lens; 1012, second lens; 1041, fifth lens; 1042, sixth lens; 1051, seventh lens; 1052, eighth lens; 1081, eleventh lens; 1082, twelfth lens; 201, thirteenth lens; 202, fifth cemented lens; 203, sixteenth lens; 204, sixth cemented lens; 205, nineteenth lens; 206, twentieth lens; 207, seventh cemented lens; 208, twenty-third lens; 209, twenty-fourth lens; 210, twenty-fifth lens; 2021, fourteenth lens; 2022, fifteenth lens; 2041, seventeenth lens; 2042, eighteenth lens; 2071, twenty-first lens; 2072, twenty-second lens; 301, eighth cemented lens; 302, twenty-eighth lens; 303, twenty-ninth lens; 304, ninth cemented lens; 305, thirty-second lens; 306, thirty-third lens; 307, tenth cemented lens; 308, thirty-sixth lens; 3011, twenty-sixth lens; 3012, twenty-seventh lens; 3041, thirtieth lens; 3042, thirty-first lens; 3071, thirty-fourth lens; 3072, thirty-fifth lens. DETAILED DESCRIPTION

[0019] To make the purposes, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. Based on the described embodiments of the present disclosure, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present disclosure.

[0020] Embodiment one: Referring to Figure 1 The embodiment discloses a double-focus objective optical system with continuous large depth of field, comprising a first cemented lens 101, a third lens 102, a fourth lens 103, a second cemented lens 104, a diaphragm, a third cemented lens 105, a ninth lens 106, a tenth lens 107, and a fourth cemented lens 108 arranged in the order of object side to image side.

[0021] The first cemented lens 101 is composed of a first lens 1011 and a second lens 1012, the second cemented lens 104 is composed of a fifth lens 1041 and a sixth lens 1042, and the fourth cemented lens 108 is composed of an eleventh lens 1081 and a twelfth lens 1082.

[0022] The first cemented lens 101 and the third lens 102 form a front fixed group, the fourth lens 103 and the second cemented lens 104 form a zoom group, and the diaphragm, the third cemented lens 105, the ninth lens 106, the tenth lens 107, and the fourth cemented lens 108 form a rear fixed group.

[0023] In the embodiment, the focal length of the front fixed group is 97.04 mm, the focal length of the zoom group is -33.47 mm, and the focal length of the rear fixed group is 24.94 mm. In the optical system, high refractive index glass is selected as the negative lens material to correct the high-order spherical aberration of the full aperture of the system, low dispersion glass is selected as the positive lens material to improve the chromatic aberration correction effect and improve the resolution of the system. Considering the difficulty and cost control of aberration correction comprehensively, the optical compensation method is adopted to realize double field observation in the embodiment. Under the premise of meeting the object image exchange principle, single lens group can also realize zoom and keep the conjugate distance unchanged, that is, the image plane position remains unchanged.

[0024] The first lens 1011 is a positive lens, the glass shape is biconvex, the material is crown glass, the focal length is 65.83 mm, and the center thickness is 6 mm; The second lens 1012 is a negative lens, the glass shape is biconcave, the material is heavy lanthanum flint glass, the focal length is -68.52 mm, and the center thickness is 3 mm; The third lens 102 is a negative lens, the glass shape is a meniscus shape, the material is crown glass, the focal length is -106.98 mm, and the center thickness is 5 mm; The fourth lens 103 is a negative lens, the glass shape is a double concave shape, the material is heavy lanthanum flint glass, the focal length is -30.08 mm, and the center thickness is 1.5 mm; The fifth lens 1041 is a positive lens, the glass shape is a double convex shape, the material is heavy lanthanum flint glass, the focal length is 33.81 mm, and the center thickness is 2.55 mm; The sixth lens 1042 is a negative lens, the glass shape is a double concave shape, the material is flint glass, the focal length is -37.81 mm, and the center thickness is 1.55 mm; The seventh lens 1051 is a negative lens, the glass shape is a meniscus shape, the material is flint glass, the focal length is -55.27 mm, and the center thickness is 1.57 mm; The eighth lens 1052 is a positive lens, the glass shape is a double convex shape, the material is crown glass, the focal length is 32.02 mm, and the center thickness is 3.1 mm; The ninth lens 106 is a positive lens, the glass shape is a double convex shape, the material is crown glass, the focal length is 52.82 mm, and the center thickness is 5.9 mm; The tenth lens 107 is a positive lens, the glass shape is a meniscus shape, the material is crown glass, the focal length is 40.02 mm, and the center thickness is 4.66 mm; The eleventh lens 1081 is a positive lens, the glass shape is a double convex shape, the material is heavy lanthanum flint glass, the focal length is 44.67 mm, and the center thickness is 2.78 mm; The twelfth lens 1082 is a negative lens, the glass shape is a double concave shape, the material is flint glass, the focal length is -15.22 mm, and the center thickness is 4.23 mm; The first gear focal length (short focus) of the optical system is 30 mm, the alignment distance is 50 m, and the covered depth of field is 30 m-132 m; the second gear focal length (long focus) is 60 mm, the alignment distance is 160 m, and the covered depth of field is 106 m-318 m.

[0025] The depth of field is calculated as follows: After the lens focuses on a certain plane (alignment plane), a certain distance before and after the plane can be clearly imaged, which is the front depth of field L1 and the rear depth of field L2, and the calculation method is as follows:

[0026]

[0027] In the formula, δ is the maximum allowable circle of confusion, f is the focal length of the objective lens, F is the F number of the aperture, and L is the distance of alignment. The maximum allowable circle of confusion δ is set to 8 microns according to at least a 2K resolution setting.

[0028] At the first gear focal length, the air gap between the front fixed group and the zoom group is 6.27 mm, and the air gap between the zoom group and the diaphragm is 26.88 mm; at the second gear focal length, the air gap between the front fixed group and the zoom group is 29.94 mm, and the air gap between the zoom group and the diaphragm is 3.21 mm.

[0029] Figure 2 The optical transfer function diagram of the optical system at the second gear focal length is shown, and the black line is the diffraction limit curve. The MTF of the full field of view is greater than 0.3@250 lp / mm. Figure 3 The optical transfer function diagram of the optical system at the first gear focal length is shown, and the black line is the diffraction limit curve. The MTF of the full field of view is greater than 0.3@250 lp / mm.

[0030] Figure 4 The point spread diagram of the optical system at the second gear focal length is shown, Figure 5 The point spread diagram of the optical system at the first gear focal length is shown. The RMS spot radius under the double field of view condition is less than 2 microns, and the GEO spot radius is less than 4 microns.

[0031] In this embodiment, the F / # (F number) of the double field of view is constant at 2.8.

[0032] The optical system described in this embodiment can match a 3840x2160 resolution detector.

[0033] Embodiment two: The embodiment discloses a double focal length objective lens optical system with continuous large depth of field, which comprises a thirteenth lens 201, a fifth cemented lens 202, a sixteenth lens 203, a sixth cemented lens 204, a nineteenth lens 205, a diaphragm, a twentieth lens 206, a seventh cemented lens 207, a twenty-third lens 208, a twenty-fourth lens 209, and a twenty-fifth lens 210 arranged in the order of the object side to the image side.

[0034] The fifth cemented lens 202 is formed by cementing the fourteenth lens 2021 and the fifteenth lens 2022, the sixth cemented lens 204 is formed by cementing the seventeenth lens 2041 and the eighteenth lens 2042, and the seventh cemented lens 207 is formed by cementing the twenty-first lens 2071 and the twenty-second lens 2072.

[0035] The thirteenth lens 201, the fifth cemented lens 202 and the sixteenth lens 203 form a front fixed group, the sixth cemented lens 204 and the nineteenth lens 205 form a zoom group, the diaphragm, the twentieth lens 206, the seventh cemented lens 207, the twenty-third lens 208, the twenty-fourth lens 209 and the twenty-fifth lens 210 form a rear fixed group.

[0036] In the embodiment, the focal length of the front fixed group is 87.95mm, the focal length of the zoom group is -27.26mm, and the focal length of the rear fixed group is 21.62mm.

[0037] The thirteenth lens 201 is a positive lens, the glass shape is biconvex, the material is crown glass, the focal length is 114.26mm, and the center thickness is 4mm; The fourteenth lens 2021 is a positive lens, the glass shape is biconvex, the material is crown glass, the focal length is 87.70mm, and the center thickness is 4.8mm; The fifteenth lens 2022 is a negative lens, the glass shape is biconcave, the material is heavy lanthanum flint glass, the focal length is -51.26mm, and the center thickness is 3mm; The sixteenth lens 203 is a positive lens, the glass shape is meniscus, the material is crown glass, the focal length is 96.40mm, and the center thickness is 5mm; The seventeenth lens 2041 is a negative lens, the glass shape is biconcave, the material is heavy lanthanum flint glass, the focal length is -28.64mm, and the center thickness is 1.5mm; The eighteenth lens 2042 is a positive lens, the glass shape is biconvex, the material is heavy flint glass, the focal length is 24.98mm, and the center thickness is 3mm; The nineteenth lens 205 is a negative lens, the glass shape is biconcave, the material is heavy lanthanum flint glass, the focal length is -23.58mm, and the center thickness is 1.5mm; The twentieth lens 206 is a positive lens, the glass shape is biconvex, the material is crown glass, the focal length is 41.81mm, and the center thickness is 2mm; The twenty-first lens 2071 is a negative lens, the glass shape is meniscus, the material is heavy flint glass, the focal length is -29.11mm, and the center thickness is 1.5mm; The twenty-second lens 2072 is a positive lens, the glass shape is biconvex, the material is crown glass, the focal length is 33.41mm, and the center thickness is 3.3mm; The twenty-third lens 208 is a positive lens, the glass shape is meniscus, the material is lanthanum flint glass, the focal length is 32.81mm, and the center thickness is 2.5mm; The twenty-fourth lens 209 is a positive lens, the glass shape is meniscus, the material is crown glass, the focal length is 37.82mm, and the center thickness is 2.5mm; The twenty-fifth lens 210 is a negative lens with a double-concave glass shape, a crown glass material, and a focal length of -17.94 mm and a center thickness of 4.5 mm.

[0038] The first gear focal length (short focus) of the optical system is 30 mm, the alignment distance is 50 m, and the covered depth of field is 30 m-132 m; the second gear focal length (long focus) is 60 mm, the alignment distance is 160 m, and the covered depth of field is 106 m-318 m. At the first gear focal length, the air gap between the front fixed group and the zoom group is 5.76 mm, and the air gap between the zoom group and the diaphragm is 22.49 mm; at the second gear focal length, the air gap between the front fixed group and the zoom group is 25.03 mm, and the air gap between the zoom group and the diaphragm is 3.22 mm.

[0039] Figure 7 The optical transfer function diagram of the optical system at the second gear focal length is shown, and the black line is the diffraction limit curve, and the full field MTF is >0.3@250lp / mm. Figure 8 The optical transfer function diagram of the optical system at the first gear focal length is shown, and the black line is the diffraction limit curve, and the full field MTF is >0.3@250lp / mm.

[0040] Figure 9 The point column diagram of the optical system at the second gear focal length is shown, Figure 10 The point column diagram of the optical system at the first gear focal length is shown. The RMS spot radius under the double field condition is less than 2 microns, and the GEO spot radius is less than 4 microns.

[0041] The F / # (F number) of the double field of the embodiment is constant at 2.8.

[0042] The optical system described in the embodiment can match a 3840x2160 resolution detector.

[0043] Embodiment three: Referring to Figure 11 The embodiment discloses a double focal length objective optical system with continuous large depth of field, which comprises an eighth cemented lens 301, a twenty-eighth lens 302, a twenty-ninth lens 303, a ninth cemented lens 304, a diaphragm, a thirty-second lens 305, a thirty-third lens 306, a tenth cemented lens 307, and a thirty-sixth lens 308 arranged in the order from the object side to the image side.

[0044] The eighth cemented lens 301 is cemented by the twenty-sixth lens 3011 and the twenty-seventh lens 3012, the ninth cemented lens 304 is cemented by the thirtieth lens 3041 and the thirty-first lens 3042, and the tenth cemented lens 307 is cemented by the thirty-fourth lens 3071 and the thirty-fifth lens 3072.

[0045] The eighth cemented lens 301 and the twenty-eighth lens 302 form a front fixed group, the twenty-ninth lens 303 and the ninth cemented lens 304 form a zoom group, and the diaphragm, the thirty-second lens 305, the thirty-third lens 306, the tenth cemented lens 307 and the thirty-sixth lens 308 form a rear fixed group.

[0046] In the embodiment, the focal length of the front fixed group is 62.02 mm, the focal length of the zoom group is -20.02 mm, and the focal length of the rear fixed group is 18.16 mm.

[0047] The twenty-sixth lens 3011 is a negative lens, the glass shape is a meniscus shape, the material is flint glass, the focal length is -49.95 mm, and the center thickness is 2.3 mm; The twenty-seventh lens 3012 is a positive lens, the glass shape is a biconvex shape, the material is crown glass, the focal length is 56.39 mm, and the center thickness is 6.2 mm; The twenty-eighth lens 302 is a positive lens, the glass shape is a biconvex shape, the material is crown glass, the focal length is 55.56 mm, and the center thickness is 5.8 mm; The twenty-ninth lens 303 is a negative lens, the glass shape is a biconcave shape, the material is heavy lanthanum flint glass, the focal length is -23.79 mm, and the center thickness is 1.2 mm; The thirtieth lens 3041 is a positive lens, the glass shape is a biconcave shape, the material is crown glass, the focal length is -31.53 mm, and the center thickness is 1.2 mm; The thirty-first lens 3042 is a negative lens, the glass shape is a biconvex shape, the material is heavy flint glass, the focal length is 41.61 mm, and the center thickness is 2 mm; The thirty-second lens 305 is a positive lens, the glass shape is a meniscus shape, the material is crown glass, the focal length is 96.12 mm, and the center thickness is 1.9 mm; The thirty-third lens 306 is a positive lens, the glass shape is a biconvex shape, the material is crown glass, the focal length is 16.51 mm, and the center thickness is 4.15 mm; The thirty-fourth lens 3071 is a negative lens, the glass shape is a meniscus shape, the material is heavy lanthanum flint glass, the focal length is -14.5 mm, and the center thickness is 3 mm; The thirty-fifth lens 3072 is a positive lens, the glass shape is a biconvex shape, the material is lanthanum flint glass, the focal length is 17.15 mm, and the center thickness is 5 mm. The thirty-sixth lens 308 is a negative lens, the glass shape is a meniscus shape, the material is crown glass, the focal length is -29.64 mm, and the center thickness is 3.5 mm.

[0048] In this embodiment, the thirty-second lens 305 and the thirty-third lens 306 are preferably aspherical glass, and the glass material can be selected from the range including D-K9, D-FK61A, D-ZK2, and D-ZK3. The aspherical surface of each aspherical surface conforms to the even non-curved surface formula:

[0049] In the formula, r is the aperture perpendicular to the optical axis direction, z is the distance from the vertex of the aspherical surface to the position of the aspherical surface along the optical axis direction at a height of r, c represents the vertex curvature of the surface (that is, the reciprocal of the radius of curvature), k is the conic coefficient, i is the aspherical order, is the coefficient of each high-order term, and 2i is the high-order of the aspherical surface. The conic coefficient and the aspherical coefficient are as follows:

[0050] The second gear focal length (long focus) is 55 mm, the alignment distance is 160 m, and the covered depth of field is 28 m-192 m; the first gear focal length (short focus) is 27.5 mm, the alignment distance is 50 m, and the covered depth of field is 100 m-392 m.

[0051] At the second gear focal length, the air gap between the front fixed group and the zoom group is 24.28 mm, and the air gap between the zoom group and the diaphragm is 1.09 mm; at the first gear focal length, the air gap between the front fixed group and the zoom group is 10.12 mm, and the air gap between the zoom group and the diaphragm is 15.25 mm.

[0052] Figure 12 The optical transfer function diagram of the optical system at the second gear focal length is shown, the black line is the diffraction limit curve, the full field of view MTF is greater than 0.3@250 lp / mm, Figure 13 The optical transfer function diagram of the optical system at the first gear focal length is shown, the black line is the diffraction limit curve, and the full field of view MTF is greater than 0.3@250 lp / mm.

[0053] Figure 14 The point spread diagram of the optical system at the second gear focal length is shown, Figure 15 The point spread diagram of the optical system at the first gear focal length is shown, and the RMS spot radius under the double field of view condition is less than 2 microns, and the GEO spot radius is less than 4 microns.

[0054] In this embodiment, the F / # (F number) of the double field of view is constant at 2.8.

[0055] The optical system described in the embodiment can match a 3840*2160 resolution detector.

[0056] The application has at least the following beneficial effects: (1) The optical compensation zooming principle is used to realize double field of view observation, and the zooming is realized while ensuring that the image quality of two focal length positions meets the 4K detector requirement (optical transfer function MTF should be >0.3@250lp / mm), and the image quality is not reduced when the position is switched, and the tracking and locking of the unmanned aerial vehicle target dynamic target are ensured. (2) The double field of view objective of the application is used for imaging different distance objects, and under the condition that the F / # is constant at 2.8, the depth of field is superimposed in two focal length working modes, and the depth of field range reaches 30m-300m, the contradiction between large aperture and large depth of field of the fixed focus lens is resolved, and only the focal length position needs to be switched after the objective correction is completed without focusing. (3) The application only needs to move the zooming group along the optical axis to realize two zooming, and the double field of view two position modes share the optical axis and the focal plane, and have the ability of fast zooming, compared with the mechanical compensation zooming system without compensation group, and have the advantages of simple structure, compactness, and good optical axis consistency.

[0057] It should be noted that according to the needs of implementation, each step / component described in the application can be split into more steps / components, or two or more steps / components or part of the operation of the steps / components can be combined into a new step / component, to realize the purpose of the application.

[0058] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the application, and is not intended to limit the application, and any modification, equivalent replacement and improvement made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. An optical system with a continuous large depth of field using dual focal length objectives, characterized in that, It includes a front fixed group, a zoom group, and a rear fixed group arranged sequentially from the object side to the image side; the zoom group can move along the optical axis, and when the zoom group is in the first position and the second position, the objective lens has a first focal length f. 短焦 Second focal length f 长焦 The first position is closer to the front fixed group than the second position. The focal length f of the front fixed group 前固定组 Satisfy: 1.00 < f 前固定组 / f 长焦 <1.75; The focal length f of the zoom group 变焦组 Satisfies: -0.67 < f 变焦组 / f 长焦 <-0.33; The focal length f of the rear fixed group 后固定组 Satisfy: 0.20 < f 后固定组 / f 长焦 <0.60; First setting focal length f 短焦 Second focal length f 长焦 satisfy: f 长焦 / f 短焦 ≥2; 25mm<f 短焦 <35mm; 50mm<f 长焦 <70mm; The objective lens has an F-number greater than or equal to 2.

8.

2. The dual-focal-length objective lens optical system with continuous large depth of field according to claim 1, characterized in that, The front fixed group includes a cemented lens and a single lens; the cemented lens is made by cementing a positive lens and a negative lens together; the single lens is a positive lens.

3. The dual-focal-length objective lens optical system with continuous large depth of field according to claim 2, characterized in that, The front fixed group single lens is a spherical lens.

4. The dual-focal-length objective lens optical system with continuous large depth of field according to claim 1, characterized in that, The zoom group includes a cemented zoom lens and a single zoom lens; the cemented zoom lens is made by cementing a positive lens and a negative lens together; the single zoom lens is a negative lens.

5. The dual-focal-length objective lens optical system with continuous large depth of field according to claim 4, characterized in that, The zoom group's single lens is a spherical lens.

6. The dual-focal-length objective lens optical system with continuous large depth of field according to claim 1, characterized in that, The rear fixed group includes an aperture stop, at least one cemented lens of the rear fixed group, and multiple single lenses of the rear fixed group; the cemented lens of the rear fixed group is made of a positive lens and a negative lens cemented together.

7. The dual-focal-length objective lens optical system with continuous large depth of field according to claim 1, characterized in that, Multiple rear-fixed single lenses include aspherical lenses.

8. The dual-focal-length objective lens optical system with continuous large depth of field according to claim 1, characterized in that, All lenses in the optical system are glass lenses.

9. A dual-focal-length objective lens with continuous large depth of field, characterized in that, Includes the optical system as described in claim 1.

10. A dual-focal-length aiming device with continuous large depth of field, characterized in that, Includes the objective lens as described in claim 9.

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